1. Field of the Invention
The present invention relates to an image photographing apparatus and an image photographing method. In particular, the present invention relates to an image photographing apparatus and an image photographing method for controllably predicting movement of the eyeball to acquire a predetermined fundus tomographic image.
2. Description of the Related Art
In recent years, OCT (Optical Coherence Tomography) apparatuses that allow fundus tomographic images to be acquired have been attracting attention. A factor in the attention paid to these apparatuses is the capability of enabling noninvasive diagnosis of the internal structure of the ocular fundus, which cannot be observed with other apparatuses. FD-OCT (Fourier Domain OCT), which has demonstrated the capability of high-speed image photographing, dominates the marketplace. The OCT apparatus includes a fundus camera and SLO (Scanning Laser Ophthalmoscopy) installed in the same apparatus to indicate which area of the ocular fundus is to undergo OCT scanning, allowing an OCT image of the vicinity of a predetermined position to be acquired.
On the other hand, in order to allow a microscopic tumor or any abnormalities to be detected during early diagnosis or early medical treatment, photographing timing and positions for OCT images need to be accurately controlled with the movement of the eyeball taken into account.
Japanese Patent Application Laid-Open No. 2004-512125 has been laid open as a patent that takes movement of the eyeball into account.
Japanese Patent Application Laid-Open No. 2009-72572 has been laid open as a patent relating to image photographing timing.
According to Japanese Patent Application Laid-Open No. 2004-512125, an OCT apparatus includes an apparatus for detecting movement of the ocular fundus. The apparatus tracks the optic disc of the ocular fundus and transmits the amount of tracking to an OCT scanner in real time to allow an OCT image of the vicinity of a predetermined position to be acquired.
Furthermore, according to Japanese Patent Application Laid-Open No. 2009-72572, control of an X-ray apparatus is synchronized with the cardiac cycle to allow a predetermined image to be acquired, thus reducing the number of image photographing operations and thus radiation exposure.
The configuration according to Japanese Patent Application Laid-Open No. 2004-512125 requires installation of a special apparatus dedicated to tracking, in addition to a fundus image photographing apparatus or a fundus tomographic image photographing apparatus. This results in the increased size of the apparatus and the need for expensive components such as a scanner for tracking. Another problem is an increase in the number of initial operations such as setting of a target for tracking (the optic disc, described above) and thus in time required for image photographing. Moreover, even with a sophisticated tracking apparatus, the eyeball moves during a process involving detection, calculation and correction, inevitably resulting in time lag.
Japanese Patent Application Laid-Open No. 2009-72572 allows image photographing to be nicely timed but fails to provide control according to independent movement of the fundus plane because the control is based on the cardiac cycle.